Among gynecologic malignancies, ovarian cancer accounts for the highest tumor-related mortality in women in the United States (Jemal et al., 2005). It is the fourth leading cause of cancer-related death in women in the U.S (Menon et al., 2005). The American Cancer Society estimated a total of 22,220 new cases in 2005 and attributed 16,210 deaths to the disease (Bonome et al., 2005). For the past 30 years, the statistics have remained largely the same—the majority of women who develop ovarian cancer will die of this disease (Chambers and Vanderhyden, 2006). The disease carries a 1:70 lifetime risk and a mortality rate of >60% (Chambers and Vanderhyden, 2006). The high mortality rate is due to the difficulties with the early detection of ovarian cancer when the malignancy has already spread beyond the ovary. Indeed, >80% of patients are diagnosed with advanced staged disease (stage III or IV) (Bonome et al., 2005). These patients have a poor prognosis that is reflected in <45% 5-year survival rate, although 80% to 90% will initially respond to chemotherapy (Berek et al., 2000). This increased success compared to 20% 5-year survival rate years earlier is, at least in part, due to the ability to optimally debulk tumor tissue when it is confined to the ovaries, which is a significant prognostic factor for ovarian cancer (Bristow R. E., 2000 and Brown et al., 2004). In patients who are diagnosed with early disease (stage I), the 5-yr survival ranges from >90 (Chambers and Vanderhyden, 2006).
Ovarian cancer comprises a heterogeneous group of tumors that are derived from the surface epithelium of the ovary or from surface inclusions. They are classified into serous, mucinous, endometrioid, clear cell, and Brenner (transitional) types corresponding to the different types of epithelia in the organs of the female reproductive tract (Shih and Kurman, 2005). Of these, serous tumors account for ˜60% of the ovarian cancer cases diagnosed. Each histologic subcategory is further divided into three groups: benign, intermediate (borderline tumor or low malignancy potential (LMP)), and malignant, reflecting their clinical behavior (Seidman et al., 2002). LMP represents 10% to 15% of tumors diagnosed as serous and is a conundrum as they display atypical nuclear structure and metastatic behavior, yet they are considerably less aggressive than high-grade serous tumors. The 5-year survival for patients with LMP tumors is 95% in contrast to a <45% survival for advanced high-grade disease over the same period (Berek et al., 2000).
Despite improved knowledge of the etiology of the disease, aggressive cytoreductive surgery, and modern combination chemotherapy, there has been only little change in mortality. Poor outcomes have been attributed to (1) lack of adequate screening tests for early disease detection, in combination with only subtle presentation of symptoms at this stage—diagnosis is frequently being made only after progression to later stages, at which point the peritoneal dissemination of the cancer limits effective treatment and (2) the frequent development of resistance to standard chemotherapeutic strategies limiting improvement in the 5-year survival rate of patients. The initial chemotherapy regimen for ovarian cancer includes the combination of carboplatin (PARAPLATIN) and paclitaxel (TAXOL). Years of clinical trials have proved this combination to be most effective after effective surgery reduces tumor volume in about 80% of the women with newly diagnosed ovarian cancer and 40% to 50% will have complete regression but studies continue to look for ways to improve it. Recent abdominal infusion of chemotherapeutics to target hard-to-reach cells in combination with intravenous delivery has increased the effectiveness. However, severe side effects often lead to an incomplete course of treatment. Some other chemotherapeutic agents include doxorubicin, cisplatin, cyclophosphamide, bleomycin, etoposide, vinblastine, topotecan hydrochloride, ifosfamide, 5-fluorouracil and melphalan. The excellent survival rates for women with early stage disease receiving chemotherapy provide a strong rationale for research efforts to develop strategies to improve the detection of ovarian cancer. Furthermore, the discovery of new ovarian cancer-related biomarkers will lead to the development of more effective therapeutic strategies with minimal side effects for the future treatment of ovarian cancer.
Presently, the diagnosis of ovarian cancer is accomplished, in part, through routine analysis of the medical history of patients and by performing physical, ultrasound and x-ray examinations, and hematological screening. Two alternative strategies have been reported for early hematological detection of serum biomarkers. One approach is the analysis of serum samples by mass spectrometry to find proteins or protein fragments of unknown identity that detect the presence or absence of cancer (Mor et al., 2005 and Kozak et al., 2003). However, this strategy is expensive and not broadly available. Alternatively, the presence or absence of known proteins/peptides in the serum is being detected using antibody microarrays, ELISA, or other similar approaches. Serum testing for a protein biomarker called CA-125 (cancer antigen-125) has long been widely performed as a marker for ovarian cancer. However, although ovarian cancer cells may produce an excess of these protein molecules, there are some other cancers, including cancer of the fallopian tube or endometrial cancer (cancer of the lining of the uterus), 60% of people with pancreatic cancer, and 20%-25% of people with other malignancies with elevated levels of CA-125. The CA-125 test only returns a true positive result for about 50% of Stage I ovarian cancer patients and has a 80% chance of returning true positive results from stage II, III, and IV ovarian cancer patients. The other 20% of ovarian cancer patients do not show any increase in CA-125 concentrations. In addition, an elevated CA-125 test may indicate other benign activity not associated with cancer, such as menstruation, pregnancy, or endometriosis. Consequently, this test has very limited clinical application for the detection of early stage disease when it is still treatable, exhibiting a positive predictive value (PPV) of <10%. And, even with the addition of ultrasound screening to CA-125, the PPV only improves to around 20% (Kozak et al., 2003). Thus, this test is not an effective screening test.
Other studies have yielded a number of biomarker combinations with increased specificity and sensitivity for ovarian cancer relative to CA-125 alone (McIntosh et al., 2004, Woolas et al., 1993, Schorge et., 2004). Serum biomarkers that are often elevated in women with epithelial ovarian cancer, but not exclusively, include carcinoembryonic antigen, ovarian cystadenocarcinoma antigen, lipidassociated sialic acid, NB/70, TAG72.3, CA-15.3, and CA-125. Unfortunately, although this approach has increased the sensitivity and specificity of early detection, published biomarker combinations still fail to detect a significant percentage of stage I/II epithelial ovarian cancer. Another study (Elieser et al., 2005) measured serum concentrations of 46 biomarkers including CA-125 and amongst these, 20 proteins in combination correctly recognized more than 98% of serum samples of women with ovarian cancer compared to other benign pelvic disease. Although other malignancies were not included in this study, this multimarker panel assay provided the highest diagnostic power for early detection of ovarian cancer thus far.
Additionally, with the advent of differential gene expression analysis technologies, for example DNA microarrays and subtraction methods, many groups have now reported large collections of genes that are upregulated in epithelial ovarian cancer (United States Patent Application published under numbers; 20030124579, 20030087250, 20060014686, 20060078941, 20050095592, 20050214831, 20030219760, 20060078941, 20050214826). However, the clinical utilities with respect to ovarian cancer of one or combinations of these genes are not as yet fully determined.
There is a need for new tumor biomarkers for improving diagnosis and/or prognosis of cancer. In addition, due to the genetic diversity of tumors, and the development of chemoresistance by many patients, there exists further need for better and more universal therapeutic approaches for the treatment of cancer. Molecular targets for the development of such therapeutics may preferably show a high degree of specificity for the tumor tissues compared to other somatic tissues, which will serve to minimize or eliminate undesired side effects, and increase the efficacy of the therapeutic candidates.
This present invention tries to address these needs and other needs.